It is known to power syringes using a gas pressure to move a stopper. In such known devices, a gas spring may provide the gas pressure required to move a stopper in the syringe and deliver a dose of medicament to a patient. When the dose of medicament has been delivered, the syringe still contains the pressurized gas that may present a hazard to the user.
In order to minimize this problem, some gas powered devices include a mechanism for venting the pressurized gas after delivery of medicament is complete.
However, in some prior art devices, tolerance stack up means that the configuration required for venting to occur may not be realized and may result in venting not taking place or taking place less effectively than desired. Additionally, in some prior art devices, tolerance stack up may also be responsible for an incomplete dose of medicament being delivered where there may be variation in the final position of the stopper relative to the forward end of the syringe barrel.
It is an object of at least one embodiment of the present invention to provide an means for venting vapor pressure from a vapor powered syringe that overcomes some of the limitations associated with the prior art. In certain embodiments, it is an object of the present invention to minimize any potential after use risk presented by a syringe powered by a vapor pressure.